Sign a transaction

This example screen displays how the Portal Provider interacts with the MPC wallet and the blockchain. The Provider has an input box to set a toAddress for the transaction of sending 0.001 ETH from our MPC wallet. The Provider then receives a signed transaction from our mobile MPC library and submits that to chain using the configured RPC url.

Ensure you have set the gateway URL correctly with Infura or Alchemy when you initialize the Portal class.

Improving signing performance

You can reduce signing latency for EVM transactions by enabling presignatures. The SDK will then pre-compute part of the MPC signing flow in the background and use that data when the user signs, without any change to your code. Enable it via the usePresignatures feature flag when creating your Portal instance. See Feature flags for details.

import React, { FC, useState } from 'react'
import { Button, Text, TextInput, View } from 'react-native'
import { usePortal, PortalRequestMethod } from '@portal-hq/core'

const NativeSendTx = () => {
  const portal = usePortal()
  const [toAddress, setToAddress] = useState('')
  const [txHash, setTxHash] = useState('')

  const handleSend = async () => {
    try {
      // Build the transaction using the simplified API
      const { transaction } = await portal.api.buildTransaction(
        toAddress,      // recipient address
        'NATIVE',       // token type (native MON)
        '0.001',        // amount
        'monad-testnet' // network
      )

      // Send the transaction
      const newTxHash = await portal.request(
        PortalRequestMethod.EthSendTransaction,
        [transaction],
        'eip155:10143',
        { signatureApprovalMemo: 'test' } // Optional signature approval memo to use for the request
      )

      setTxHash(newTxHash)
      setToAddress('')
    } catch (error) {
      console.error('Failed to send transaction:', error)
    }
  }

  return (
    <View>
      <Text>Send 0.001 MON</Text>
      <TextInput
        onChangeText={setToAddress}
        placeholder="Enter recipient address"
        value={toAddress}
      />

      <View style={{ marginTop: 10 }}>
        <Button
          disabled={!portal || !toAddress || !toAddress.length}
          onPress={handleSend}
          title="Send MON"
        />
      </View>

      {txHash && txHash.length > 0 && (
        <View>
          <Text>Successfully sent transaction!</Text>
          <Text>Transaction Hash: {txHash}</Text>
        </View>
      )}
    </View>
  )
}

export default NativeSendTx

Signing a User Operation

If your client uses Account Abstraction, you can sign an ERC-4337 User Operation using the eth_signUserOperation method. This signs the User Operation without submitting it on-chain, returning the signature directly.

import React from 'react'
import { usePortal, PortalRequestMethod } from '@portal-hq/core'

const SignUserOperation = () => {
  const portal = usePortal()

  const handleSignUserOperation = async () => {
    const chainId = 'eip155:11155111' // Ethereum Sepolia

    const address = await portal.address
    if (!address) return

    const userOp = {
      sender: address,
      nonce: '0x0',
      callData: '0x',
      callGasLimit: '0x5208',
      verificationGasLimit: '0x5208',
      preVerificationGas: '0x5208',
      maxFeePerGas: '0x1',
      maxPriorityFeePerGas: '0x1',
    }

    try {
      const signature = await portal.request(
        PortalRequestMethod.EthSignUserOperation,
        [userOp],
        chainId,
      )

      console.log('✅ Signature:', signature)
    } catch (error) {
      console.error('❌ Failed to sign UserOperation:', error)
    }
  }

  return null
}

export default SignUserOperation

User Operation Parameters:

Name	Type	Description
`sender`	`string`	The address of the smart contract account
`nonce`	`string`	Anti-replay parameter (hex-encoded)
`callData`	`string`	The data to pass to the `sender` during the main execution call (hex-encoded)
`callGasLimit`	`string`	Gas limit for the main execution call (hex-encoded)
`verificationGasLimit`	`string`	Gas limit for the verification step (hex-encoded)
`preVerificationGas`	`string`	Gas paid for pre-verification (hex-encoded)
`maxFeePerGas`	`string`	Maximum fee per unit of gas (hex-encoded)
`maxPriorityFeePerGas`	`string`	Maximum priority fee per unit of gas (hex-encoded)

You can also pass a signature approval memo and control gas sponsorship:

const signature = await portal.request(
  PortalRequestMethod.EthSignUserOperation,
  [userOp],
  chainId,
  {
    signatureApprovalMemo: 'Approve UserOp',
    sponsorGas: true,
  },
)

Signing a Solana Transaction

You can use our provider just like you do with Ethereum with Solana. Simply specify the method and the chainId for Solana. This example uses solana/web3.js to construct a transaction object to sign and pass to the multi-chain provider.

Solana Provider Methods

sol_signMessage
sol_signTransaction
sol_signAndSendTransaction
sol_signAndConfirmTransaction

import React, { useState } from 'react'
import { Button, Text, TextInput, View } from 'react-native'
import { usePortal, PortalRequestMethod } from '@portal-hq/core'

const SolanaSendTx = () => {
  const portal = usePortal()
  const [toAddress, setToAddress] = useState('')
  const [txHash, setTxHash] = useState('')

  const handleSend = async () => {
    try {
      const chainId = 'solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1' // Solana Devnet

      // Build the transaction using the simplified API
      const { transaction } = await portal.api.buildTransaction(
        toAddress,         // recipient address
        'NATIVE',          // token type (native SOL)
        '0.001',           // amount in SOL
        chainId            // CAIP-2 Chain, or friendly name like "solana-devnet"
      )

      // Send the transaction
      const newTxHash = await portal.request(
        PortalRequestMethod.SolSignAndSendTransaction,
        [transaction], // transaction is already base64 encoded
        chainId,
        { signatureApprovalMemo: "test" } // Optional signature approval memo to use for the request
      )

      setTxHash(newTxHash)
      setToAddress('')
    } catch (error) {
      console.error('Failed to send transaction:', error)
    }
  }

  return (
    <View>
      <Text>Send 0.001 SOL</Text>
      <TextInput
        onChangeText={setToAddress}
        placeholder="Enter recipient address"
        value={toAddress}
      />

      <View style={{ marginTop: 10 }}>
        <Button
          disabled={!portal || !toAddress || !toAddress.length}
          onPress={handleSend}
          title="Send SOL"
        />
      </View>

      {txHash?.length > 0 && (
        <View>
          <Text>Successfully sent transaction!</Text>
          <Text>Transaction Hash: {txHash}</Text>
        </View>
      )}
    </View>
  )
}

export default SolanaSendTx

Raw sign

You can now utilize our SDK to generate raw signatures that are generated using the underlying key share without adding any chain specific formatting to the signature. This effectively unlocks your ability to use the Portal SDK with any chain that uses SECP256K1 or ED25519.

import { PortalRequestMethod } from '@portal-hq/core'

const handleRawSign = async () => {
  try {
    const signedMessage = await portal.request(
      PortalRequestMethod.RawSign,
      ['74657374'], // Must be in hex format, e.g. "test" is "74657374" in hex.
      'eip155:10143', // choose the chainId eip155 = secp256k1, solana = ed25519, monad = secp256k1
      { signatureApprovalMemo: 'Optional memo for this signature' } // Optional
    )
    console.log('✅ Signed message', signedMessage)
  } catch (error) {
    console.error(error)
    console.log('❌ Failed to sign')
    throw error
  }
}

Estimating Gas

By default, Portal will estimate and populate the gas property in a transaction object if the property is undefined. To estimate the gas value manually use the eth_estimateGas RPC call and pass in your transaction as the parameter.

import { PortalRequestMethod } from '@portal-hq/core'

// Build a transaction to be sent
const transaction = {
  from: await portal.keychain.getAddress(),
  to: toAddress,
  value: BigNumber.from('1').toHexString(), // Example value
}

// Use the Portal Web3 Provider to make requests
const gas = await portal.request(
  PortalRequestMethod.EthEstimateGas,
  [transaction],
  'eip155:10143',
  { signatureApprovalMemo: 'test' } // Optional signature approval memo to use for the request
)

console.log(gas) // "0x5208"

And now you are signing transactions with Portal! 🚀 Next, we’ll explore how to simulate a transaction so that you can create smoother experiences for your users.

Getting Started

SDKs

APIs

Integrations

Resources

Sign a transaction

Improving signing performance

Signing a User Operation

Signing a Solana Transaction

Solana Provider Methods

Raw sign

Estimating Gas

​Improving signing performance

​Signing a User Operation

​Signing a Solana Transaction

​Solana Provider Methods

​Raw sign

​Estimating Gas

Improving signing performance

Signing a User Operation

Signing a Solana Transaction

Solana Provider Methods

Raw sign

Estimating Gas